1. Field of the Invention
The present invention relates to a numerical controller that controls a machine tool and, more particularly, to a numerical controller capable of specifying a halt point.
2. Description of the Related Art
There is a case where a halt of work machining by a machine tool which has not been planned before start of the machining becomes necessary during the machining. Examples of such a case include: a case where it is necessary to observe a machining state; a case where interruption by a different work (machining) occurs; a case where it is necessary to perform replacement of a maintenance part during the machining (replacement of a wire in the case of, e.g., wire discharge machining); a case where it is necessary to respond to a warning during machining (collection of a used wire, in the case of, e.g., wire discharge machining); a case where it is necessary to wait for reduction of a raised temperature of machining liquid or machine tool; a case where it is necessary to remove machining chips or contamination of machining liquid; a case where it is necessary to match the machining operation time with working time of an operator; and the like.
For example, an automatic operation is halted using a feed-hold stop or a single block stop function (see JP 1-229305 A), and machining is halted using a halt command for halting a machining program (see JP 2003-001547 A) or using a sequence number collation stop function. A machining flaw or tool damage may occur due to halt and subsequent resume operations. Therefore, an operator needs to perform the feed-hold stop or single block stop function after waiting, while observing the machining state, until a favorable condition is reached.
As a method of halting an automatic operation of the machine tool, there is known one that previously inserts a halt command into a machining program. However, in this method, more halt commands than are necessary need to be inserted for allowing execution of an unplanned halt operation. Further, the automatic operation cannot be halted in a block into which the halt command is not inserted.
In order to halt the automatic operation using the feed-hold stop or single block stop function, it is necessary to execute a halt operation at a convenient timing so that the machining flaw or tool damage does not occur due to halt and subsequent resume operations. Particularly, in a machining program composed of minute blocks, it is necessary to execute the halt operation within a short period of time in a timely fashion. Further, in a machining process to be performed at a low speed, like an electrical discharge machining process, sometimes an operator is forced to wait for a long time until a point at which the machining process can be halted is reached.
In order to halt the automatic operation using the halt command (M00/M01, etc.), it is necessary to previously insert the halt command into the machining program at a plurality of points before start of the machining, on the assumption that the operation is halted. This takes a lot of time and effort in creation of the machining program. Further, the automatic operation cannot be halted in a command block into which the halt command is not inserted.
In order to halt the automatic operation using the sequence number collation stop function, it is necessary to previously set, before start of the machining, a command block in which the halt is allowed to occur. Therefore, it is impossible to cope with a case where there occurs an additional need to halt the operation after start of the machining.
When minute paths successively appear in the machining program at time of checking the machining program, it is necessary to perform a start-up operation repeatedly in the single block stop function, making the operation complicated.